I did think it was somewhat of a long-shot. 
I saw ‘api reference’ and thought I’d chance it.
I think my ridiculously wide-of-the-mark answer may have already revealed my inexperience in this area, but (at the risk of doing exactly the same thing again 
) I think there are some good general pointers in the Developing Discourse Themes & Theme Components if you’ve not seen that already?
But hopefully someone more knowledgable will turn up and be able to offer something actually helpful. 